This invention relates to an apparatus for cutting ocular lens materials, as well as a chuck to be used with that apparatus. More specifically, this invention relates to an apparatus for cutting ocular lens materials (hereinafter referred to simply as "lens materials") in the process of producing ocular lenses such as contact lenses and intraocular lenses. The invention also relates to a chuck for securing lens materials to said cutting apparatus.
Conventional chucks for securing lens materials to cutting apparatus are classified as a "drawbar" type and a "vacuum" type. A chuck of the drawbar type is shown in FIG. 8. The chuck generally indicated by 51 comprises a collet chuck 52 and a tubular holder 53 with a bottom that holds the collet chuck 52 by surrounding it. The holder 53 has a hollow main shaft 54 connected thereto for transmitting a rotational force from a rotating drive unit Al to the holder 53. The collet chuck 52 has a rod-like drawbar 55 connected to its basal end for transmitting a reciprocal force from a reciprocating drive unit R to the collet chuck 52.
The drawbar 55 is inserted into the hollow portion of the main shaft 54 in such a way as to form a slight clearance; the drawbar 55 is also inserted into a hole 53a in the bottom of the holder 53.
The collet chuck 52 has a plurality of fingers 52a that are formed in such a manner as to hold a lens material in position. The back side of each finger 52a is tapered or the collector chuck 52 has such a shape that its outside diameter decreases gradually from the finger 52a toward the base.
When the collet chuck 52 is pulled together with the drawbar 55 by means of the reciprocating drive unit R, the tapered back side of each finger 52a is pressed against the peripheral edge of the opening in the holder 53, whereupon the resulting counterforce causes the fingers 52a to close to grip the lens material L which is placed in the collet chuck 52.
Conversely, if the collet chuck 52 is pushed out of the holder 53, the fingers 52a will return to the initial open state, causing the lens material L to be disengaged from the collet chuck 52.
A chuck of the vacuum type is shown in FIG. 9. The chuck generally indicated by 61 is of a tubular form that has a gas passageway 62 bored through it along the central axis. The chuck 61 has one end of a main shaft 63 connected thereto for transmitting a rotational force from a rotating drive unit A2 to the chuck 61. The main shaft 63 has a gas passageway 64 bored through it along the central axis that communicates with the gas passageway 62 through the chuck 61. The main shaft 63 has an air aspirator V provided on the other end that communicates with the gas passageway 64.
If a lens material L is placed at the end of the chuck 61 to close the gas passageway 62 and when the air aspirator V is actuated, a negative pressure is established within the gas passageway 62, whereupon the lens material is fixed on the chuck 61 by being sucked to its end.
In the case of a chuck of the first type, the drawbar 55 will rotate in synchronism with the main shaft 54. Since the drawbar 55 is an elongated member, all or part of it will often rotate eccentrically and, in an extreme case, it may contact the inner surface of the hollow portion of the main shaft 54. As a result, vibrations will occur to lower the precision of the cut surface of the lens material.
In the case of a chuck of the second type, air must be sucked with a sufficient force to hold the lens material even in the midst of cutting it with a blade applied. Hence, a bulky air aspirator is necessary, leading to a higher equipment cost. A further problem with the vacuum type is that if the air aspirator stops operating for some reason such as power failure, the lens material will drop.